Electrical receptacle

ABSTRACT

An electrical receptacle adapted to be secured in a power outlet box for interconnecting the prongs of a plug receptacle or wall switch to the powerlines leading into the outlet box. The receptacle has a plastic casing including a pair of metallic tubular conductors extending along opposite sidewalls of the casing against the backwall of the casing. Powerlines extend through the tubular conductors and are secured thereto by screws mounted transversely in the sidewalls of the tubular conductors. A plastic cover plate closes the receptacle and has three apertures respectively aligned with two conductor prongs secured to the tubular conductors and a third ground prong secured in the casing between the tubular conductors. Two additional tubular conductor elements are also secured in the casing, each having a screw for securing wires therein to enable the receptacle to accommodate various wiring or switch connections. Apertures are provided in the casing in axial alignment with the tubular conductors to facilitate insertion of wires therein. Similarly, apertures are provided in the casing to expose the screws for adjustment externally of the casing.

United States Patent [72] lnventor Angelo Castellano 2710 Walnut St., Tampa, Fla. 33607 [211 App]. No. 785,264 [22] Filed Dec. 19, 1968 [45] Patented Sept. 28, 1971 [54] ELECTRICAL RECEPTACLE 19 Claims, 5 Drawing Figs.

52 0.5. Ci; 339/122, 339/272 A [51] Int. Cl H01! 13/60 [50] Field of Search 339/ l22 [56] References Cited UNITED STATES PATENTS 2,433,917 l/1948 McCartney 339/122 2,920,303 l/l960 Johnson 339/159 X 3,038,141 6/1962 Chiuchiolo. 339/122X 3,157,732 11/1964 Richards 339/95 DX 3,451,037 6/1969 l-lerrli 339/122 X 2,707,774 5/1955 Keller 339/2721 X Primary Examiner-Ernest R. Purser Attorney-Beveridge & DeGrandi ABSTRACT: An electrical receptacle adapted to be secured in a power outlet box for interconnecting the prongs of a plug receptacle or wall switch to the powerlines leading into the outlet box; The receptacle has a plastic casing including a pair of metallic tubular conductors extending along opposite sidewalls of the casing against the backwall of the casing. Powerlines extend through the tubular conductors and are secured thereto by screws mounted transversely in the sidewalls of the tubular conductors. A plastic cover plate closes the receptacle and has three apertures respectively aligned with two conductor prongs secured to the tubular conductors and a third ground prong secured in the casing between the tubular conductors. Two additional tubular conductor elements are also secured in the casing, each having a screw for securing wires therein to enable the receptacle to accommodate various wiring or switch connections. Apertures are provided in the casing in axial alignment with the tubular conductors to facilitate insertion of wires therein. Similarly, apertures are provided in the casing to expose the screws for adjustment externally of the casing.

PATENTED .SEP-28 lHYI SHEET 1 OF 2 INVENTOR f ANGELO casnzumo BY ATTORNEYS PATENTEI] SEP28 m1 SHEET 2 [1F 2 a m m 'Fies INVENTOR BY ANGELO CASTELLANO 50 51 w ,4

ATTORNEYS ELECTRICAL RECEI'IACLE OBJECTS OF THE INVENTION This invention relates to an electric receptacle which may be installed in a power outlet box such as for example in a home, to connect either a wall switch or plug receptacle to the powerlines leading into the outlet box.

It, is an object of the present invention to provide a device for securing a switch or plug receptacle in a wall in connection with powerlines without requiring any manipulation or alteration of the powerlines thereby avoiding hazard as well as extremely reducing the time required to make the connection.

A;further object of the present invention is to provide such a receptacle which will accommodate various types of switches and wiring systems in addition to conventional wiring the toggle switches. Included herein is such a receptacle also having provision for a ground connection.

A still further object of the present invention is to provide such a receptacle wherein wires may be easily and firmly secured without fear of breaking any parts of the receptacle. Included herein is provision of such a receptacle also providing convenient access to adjusting screws used to fasten wires in place.

Yet another object of the present invention is to provide such a receptacle that may be easily installed in conventional outlet boxes in the home.

Other objects and advantages will become apparent from the following more detailed description taken in connection with .the drawings in which:

FIG. 1 is an exploded, perspective view of a receptacle embodying the invention, a power outlet box, and a plug receptacle;

FIG. 2 is a perspective view of a wall switch which may be plugged into the receptacle of the invention in place of the wall plug receptacle shown in FIG. 1;

FIG. 3 is an exploded perspective view of the receptacle with certain portions cut away to show internal parts thereof;

FIG. 4 is a vertical cross-sectional view taken through the power outlet box showing one side of the receptacle with a wall switch plugged therein and powerlines connected to the receptacle; and

FIG. 5 is across sectional view taken generally along lines 4-4 of FIG. 5 but showing the wall switch removed from the receptacle.

DETAILED DESCRIPTION Referring now-to the drawings in detail, FIG. 1 shows a conventional power outlet box having apertured flanges 12 projecting from the top and bottom walls 14 and 16 thereof for securement to a wall 18 (see FIG. 4) with the box projecting inwardly into a compartment in the wall in conventional manner. As illustrated in FIG. 4, bottom wall 16 of the outlet box is apertured to receive powerlines 20 as well as a ground line 22. A cable 24 encases lines 20 and 22 externally of the power outlet box as shown in FIG. 4.

A receptacle generally designated 30 embodying the present invention is adapted to be secured in outlet box 10 by means of apertured brackets 32 which receive screws 34 extending through flanges 12 of the outlet box. Receptacle 30 may be employed to alternatively connect for example a plug or convenience receptacle generally designated 36 or a wall switch generally designated 38 to powerlines 20 and ground line 22. The leg portions 33 of brackets 32 are sufficiently dimensioned to recess receptacle 30 in the mouth of outlet box 10 thus providing a space outwardly of receptacle 30 for receiving wall switch 38 or convenience receptacle 36 as illustrated in FIG. 4.

Plug receptacle 36 and wall switch 38 each have a pair of conductor prongs 36a and 38a and also a ground prong 36b, 38b which are connected therein in any suitable manner to be received in engagement with corresponding prongs in receptacle 30 as will be described. The remaining portions of wall switch 38 and plug receptacle 36 may be conventional, forming no part of the present invention, and therefore need not be described further. Although plug receptacle 36 and switch 38 are secured through their respective flanges 36c and 38c by the same screws 34 employed to fasten receptacle 30, separate fasteners and brackets (not shown) may be employed so that when the plug receptacle 36 or switch 38 is removed from receptacle 30 as will be described, the receptacle 30 will remain secured in the outlet box 10. Additionally it will be ap preciated that when converting from the plug receptacle 36 to switch 38, different wiring will be required in the electrical system controlled by the switch.

In the specific embodiment shown receptacle 30 has a plastic casing including a backwall 40, two parallel sidewalls 42, 44 projecting forwardly from the backwall, and top and bottom walls 46, 48 each of which are shown as stepped in shape. A rectangular plastic cover plate generally designated 50 is provided to close the casing in the shown embodiment. Cover plate 50 has top and bottom apertures 52 for receiving screws 54 which fit into threaded passages 56 in the receptacle casing. In order to provide access to conductor prongs in the receptacle which will be subsequently described, cover plate 50 is apertured at 58 and 60; apertures 58 dimensioned to receive positive and negative pole conductor prongs while aperture 60 being dimensioned to receive a ground prong. Although not shown, cover plate 50 may be formed integral with the side and top and bottom walls of the casing by any suitable molding operation.

Secured within the receptacle casing are a pair of tubular metallic conductors generally designated 70 and 72 which extend along the inner surfaces of sidewalls 42, 44 at back wall 40 of the casing. Tubular conductors 70, 72 in the shown embodiment extend throughout between the upper section 480 of the casing bottom wall and the lower section 460 of the casing top wall and are secured therein in any suitable manner such as by molding or otherwise. Powerlines 20 are introduced into the receptacle casing through apertures 74 either in the top or bottom walls of the casing and then axially inserted through the hollow spaces in the tubular conductors 70, 72 as partly illustrated in FIG. 4.

To secure wires 20 in firm contact with tubular conductors 70, 72 without requiring contact with wires 20 by the fingers,

metallic screws 76 are threaded transversely in the outer walls of tubular conductors 70, 72 to be movable transversely in the tubular conductors to clamp wires 20 to a portion of the tubular conductors upon advancement of the screws. In the shown embodiment, each tubular conductor has two such screws 76 located generally at the opposite ends thereof for accominodating a plurality of wires. Sidewalls 42 and 44 of the receptacle casing are apertured at 78 to provide access to screws 76 from points externally of the casing. Conductors 70, 72 may be formed of any suitable conductor material such as brass-coated copper and in any suitable shape although in the shown embodiment, the conductors have a generally rectangular cross section with the inner sides thereof being beveled as shown in order to facilitate installation and securement of the wires therein.

Electrical connection between tubular conductors 70, 72 and the wall switch 38 or plug receptacle 36 is made by conductor posts or prongs generally designated 80 respectively secured to tubular conductors 70, 72 to project therefrom towards the opening in the casing as shown. In the specific embodiment, prongs 80 are secured to the inner walls of the tubular conductors generally at the bottom portions thereof. The connection between the ground prong of the wall switch or plug receptacle and the ground wire 22 is made through a tubular ground prong 82 secured in the casing above and between prongs 80. Ground prong 82 is secured to a depending flat conductor element 84 which extends upwardly through an aperture in the lower section 46a of the top casing wall where it bends outwardly at 85 for receiving a screw 86 employed to connect ground wire 22 thereto externally of the receptacle casing.

In order to accommodate different types of switches and wiring, the receptacle is provided with additional conductors generally designated 90, 92 which may have the same cross section as conductors 70, 72 but are much shorter in axial length. Conductors 90, 92 are suitably secured to the lower section of bottom casing wall 48 with their axes at right angles to the axes of conductors 70, 72 as illustrated in FIG. 3. Screws 94 are mounted in the outer walls of conductors 90, 92 for clamping wires (not shown) therein against the inner wall sections of conductors 90, 92. The sidewalls 42, 44 of the casing are also apertured at 96 to provide access to screws 94 from points outside of the casing. Wires may be lead into the casing for securement in and against conductors 90, 92 through apertures 98 (one shown) in the backwall 40 of the casing.

According to one method of installing the receptacle 30 and the convenience receptacle 36 in the outlet box 10, assuming the cover plate 50 is in place in the receptacle 30, the convenience receptacle 36 is plugged into the receptacle 30 and then the unit is inserted into the outlet box and secured therein by means of screws 34 passing through flanges 38c, 32 and 12. Assuming the ends of wires 20 are bare, these wires are inserted upwardly through the outlet box 10 and then through apertures 74 in the bottom wall section 480 of the easing and then upwardly through the tubular conductors 70 and 72 respectively. Screws 76 may then be advanced in conductors 70 and 72 to firmly clamp the wires against wall portions of the conductors 70 and 72. if a ground wire such as 22 is present in the installation, this wire may be connected to the screw 86 of the receptacle 30 prior to insertion of the receptacle 30 into the outlet box 10. It will be understood that the wall switch 38 may be similarly installed.

1 claim:

1. An electrical receptacle comprising a casing made of nonconductive material and defining a compartment, a hollow, metallic tubular conductor secured to the casing in said compartment for receiving wires, an adjustable conductor element, means mounting said adjustable conductor element in one wall of said tubular conductor for movement transversely of the axial direction of said tubular conductor for engaging a wire placed axially in the tubular conductor to hold the wire against a portion of said tubular conductor, said receptacle including at at least three of said tubular conductors secured to the casing in said compartment for receiving said wires, each of said tubular conductors having mounted therein an adjustable conductor element for securing wires against the conductor, a pair of conductor prongs secured to two of said tubular conductors respectively for engagement with prongs on a wall switch or a plug receptacle. A third prong secured to said casing in said compartment for connection to a ground prong of a wall switch or plug receptacle, said casing including a cover plate closing said compartment, said cover plate having apertures aligned with said prongs for receiving corresponding prongs of a wall switch or plug receptacle to interengage the latter prongs with the prongs in the casing.

2. The receptacle defined in claim 1 wherein said casing includes opposite walls situated adjacent said tubular conductors, said walls having apertures in alignment with said adjustable conductor elements for providing access to the latter externally of the casing.

3. The electrical receptacle defined in claim 2 wherein said walls of said casing constitute sidewalls extending generally parallel to each other, said two tubular conductors extend along the inner surfaces of said sidewalls in parallel relationship.

4. The electrical receptacle defined in claim 3 wherein said two tubular conductors each contain an additional adjustable conductor element and means for mounting the additional adjustable conductor element in the wall thereof for movement transverse to the axis of the tubular conductors for securing additional wires to said tubular conductors.

5. The electrical receptacle defined in claim 4 wherein said adjustable conductor elements are screws and wherein said means mounting said adjustable conductor elements are threads in the walls of said tubular conductors.

6. An electrical receptacle comprising a casing made of nonconductive material and defining a compartment, a hollow, metallic tubular conductor secured to the casing in said compartment for receiving wires, an adjustable conductor element, means mounting said adjustable conductor element in one wall of said tubular conductor for movement transversely of the axial direction of said tubular conductor to hold the wire against a portion of said tubular conductor, said casing including opposite sidewalls and a pair of said tubular conductors extending along the sidewalls in the compartment and a third tubular conductor adjacent one of the sidewalls but with its axis at an angle to the axes of said pair of said tubular conductors, each conductor having a metallic screw transversely mounted in its sidewall for securing a wire therein.

7. The electrical receptacle defined in claim 6 further including a fourth tubular conductor mounted to the casing in the compartment thereof in opposed position to said third tubular conductor and adjacent the other sidewall of said casing.

8. The electrical receptacle defined in claim 7 wherein the axes of said third and fourth tubular conductors are parallel and extend an angle to the axes of said first and second tubular conductors.

9. An electrical receptacle for connecting a plug receptacle or a switch to a source of power, the receptacle comprising in combination; a plastic casing including a backwall and opposite sidewalls projecting forwardly from the backwall to define a compartment, a pair of metallic tubular conductors extending longitudinally in the compartment adjacent the backand sidewalls for receiving wires in the hollows thereof, said tubular conductors having outer walls including screw threads and screws received in said threads for movement transversely across the spaces in said tubular conductors for securing a wire against a portion of said tubular conductors, two conductor prongs respectively secured to said tubular conductors and projecting at an angle thereto, and a front wall closing the compartment in the casing, said front wall having a pair of apertures aligned with said prongs for receiving the prongs of a wall switch or a plug receptacle for interengaging the latter with the prongs in the compartment.

10. The receptacle defined in claim 9 further including a third, ground prong, and means securing said ground prong in the compartment between said tubular conductors, said front wall having a third aperture aligned with said ground prong for receiving a ground prong of a wall switch or plug receptacle to interengage the latter with the ground prong in the casing.

11. The electrical receptacle defined in claim 10 wherein said casing has a top wall with an aperture, and said means securing said ground prong includes a conductor extending through said aperture in said top wall.

12. The electrical receptacle defined in claim 10 further including third and fourth tubular conductors secured in the casing adjacent the sidewalls thereof and each having a threaded passage with a screw threaded therein for securing a wire against a portion thereof.

13. The receptacle defined in claim 12 wherein said casing includes a stepped bottom wall including an upper level and a lower level, said first and second tubular conductors extending above the top level adjacent said backwall, said third and fourth tubular conductors being located on said bottom level.

14. The receptacle defined in claim 13 wherein said third and fourth tubular conductors have axes extending at an angle to the axes of said first and second tubular conductors.

15. The receptacle defined in claim 9 wherein said sidewalls have apertures overlying the screws in said tubular conductors to provide access to the screws from points externally of the casing.

16. The receptacle defined in claim 15 wherein said casing has apertures axially aligned with said tubular conductors to permit wires to be inserted through said casing and into said tubular conductors from points located externally of the casmg.

17. An electrical receptacle for connecting a plug receptacle or a switch to a source of power, the receptacle comprising in combination; a plastic casing including a backwall and opposite sidewalls projecting forwardly from the backwall to define a compartment, a pair of tubular conductors extending longitudinally in the compartment adjacent the backand sidewalls for receiving wires to establish a electrical connection therewith, said conductors each having adjustable means for releasably securing wires to the conductors respectively, two conductor prongs respectively secured to said conductors and projecting at an angle thereto, a third ground prong, means securing said ground prong in the compartment between said first two conductors, and a front wall closing the compartment in the casing, said front wall having a pair of apertures aligned with said conductor prongs for receiving the prongs of a wall switch or a plug receptacle for interengaging the latter with the conductor prongs in compartment, said front wall having a third aperture aligned with said ground prong for receiving a ground prong of a wall switch or plug receptacle to interengage the latter with the ground prong in the casing.

18. An electrical receptacle comprising a casing made of nonconductive material and defining a compartment, a hollow, metallic tubular conductor secured to the casing in said compartment for receiving wires, an adjustable conductor element, means mounting said adjustable conductor element in one wall of said tubular conductor for movement transversely of the axial direction of said tubular conductor for engaging a wire placed axially in the tubular conductor to hold the wire against a portion of said tubular conductor, said casing having an aperture in axial alignment with said tubular conductor to permit a wire to be inserted through the casing and into the tubular conductor from a point externally of the casing.

19. An electrical receptacle for connecting a plug receptacle or a switch to a source of power, the receptacle comprising in combination; a casing made from nonconductive material and having means defining a compartment, a pair of conductors in the compartment for connection to wires to establish electrical connection therebetween, said conductors each having means for releasably securing wires to the conductors respectively, two conductor prongs respectively secured to said conductors and projecting at an angle thereto, a third ground prong, means securing said ground prong in the compartment between said first two conductors, and a front wall closing the compartment, said front wall having a pair of apertures aligned with said conductor prongs for receiving the prongs of a wall switch or a plug receptacle for interengaging the latter with the conductor prongs in the compartment, said front wall having a third aperture aligned with said ground prong for receiving a ground prong of a wall switch or plug receptacle to interengage the latter with the ground prong and the casing. 

1. An electrical receptacle comprising a casing made of nonconductive material and defining a compartment, a hollow, metallic tubular conductor secured to the casing in said compartment for receiving wires, an adjustable conductor element, means mounting said adjustable conductor element in one wall of said tubular conductor for movement transversely of the axial directIon of said tubular conductor for engaging a wire placed axially in the tubular conductor to hold the wire against a portion of said tubular conductor, said receptacle including at at least three of said tubular conductors secured to the casing in said compartment for receiving said wires, each of said tubular conductors having mounted therein an adjustable conductor element for securing wires against the conductor, a pair of conductor prongs secured to two of said tubular conductors respectively for engagement with prongs on a wall switch or a plug receptacle. A third prong secured to said casing in said compartment for connection to a ground prong of a wall switch or plug receptacle, said casing including a cover plate closing said compartment, said cover plate having apertures aligned with said prongs for receiving corresponding prongs of a wall switch or plug receptacle to interengage the latter prongs with the prongs in the casing.
 2. The receptacle defined in claim 1 wherein said casing includes opposite walls situated adjacent said tubular conductors, said walls having apertures in alignment with said adjustable conductor elements for providing access to the latter externally of the casing.
 3. The electrical receptacle defined in claim 2 wherein said walls of said casing constitute sidewalls extending generally parallel to each other, said two tubular conductors extend along the inner surfaces of said sidewalls in parallel relationship.
 4. The electrical receptacle defined in claim 3 wherein said two tubular conductors each contain an additional adjustable conductor element and means for mounting the additional adjustable conductor element in the wall thereof for movement transverse to the axis of the tubular conductors for securing additional wires to said tubular conductors.
 5. The electrical receptacle defined in claim 4 wherein said adjustable conductor elements are screws and wherein said means mounting said adjustable conductor elements are threads in the walls of said tubular conductors.
 6. An electrical receptacle comprising a casing made of nonconductive material and defining a compartment, a hollow, metallic tubular conductor secured to the casing in said compartment for receiving wires, an adjustable conductor element, means mounting said adjustable conductor element in one wall of said tubular conductor for movement transversely of the axial direction of said tubular conductor to hold the wire against a portion of said tubular conductor, said casing including opposite sidewalls and a pair of said tubular conductors extending along the sidewalls in the compartment and a third tubular conductor adjacent one of the sidewalls but with its axis at an angle to the axes of said pair of said tubular conductors, each conductor having a metallic screw transversely mounted in its sidewall for securing a wire therein.
 7. The electrical receptacle defined in claim 6 further including a fourth tubular conductor mounted to the casing in the compartment thereof in opposed position to said third tubular conductor and adjacent the other sidewall of said casing.
 8. The electrical receptacle defined in claim 7 wherein the axes of said third and fourth tubular conductors are parallel and extend an angle to the axes of said first and second tubular conductors.
 9. An electrical receptacle for connecting a plug receptacle or a switch to a source of power, the receptacle comprising in combination; a plastic casing including a backwall and opposite sidewalls projecting forwardly from the backwall to define a compartment, a pair of metallic tubular conductors extending longitudinally in the compartment adjacent the back- and sidewalls for receiving wires in the hollows thereof, said tubular conductors having outer walls including screw threads and screws received in said threads for movement transversely across the spaces in said tubular conductors for securing a wire against a portion of said tubular conductors, two conductor prongs respectively secuRed to said tubular conductors and projecting at an angle thereto, and a front wall closing the compartment in the casing, said front wall having a pair of apertures aligned with said prongs for receiving the prongs of a wall switch or a plug receptacle for interengaging the latter with the prongs in the compartment.
 10. The receptacle defined in claim 9 further including a third, ground prong, and means securing said ground prong in the compartment between said tubular conductors, said front wall having a third aperture aligned with said ground prong for receiving a ground prong of a wall switch or plug receptacle to interengage the latter with the ground prong in the casing.
 11. The electrical receptacle defined in claim 10 wherein said casing has a top wall with an aperture, and said means securing said ground prong includes a conductor extending through said aperture in said top wall.
 12. The electrical receptacle defined in claim 10 further including third and fourth tubular conductors secured in the casing adjacent the sidewalls thereof and each having a threaded passage with a screw threaded therein for securing a wire against a portion thereof.
 13. The receptacle defined in claim 12 wherein said casing includes a stepped bottom wall including an upper level and a lower level, said first and second tubular conductors extending above the top level adjacent said backwall, said third and fourth tubular conductors being located on said bottom level.
 14. The receptacle defined in claim 13 wherein said third and fourth tubular conductors have axes extending at an angle to the axes of said first and second tubular conductors.
 15. The receptacle defined in claim 9 wherein said sidewalls have apertures overlying the screws in said tubular conductors to provide access to the screws from points externally of the casing.
 16. The receptacle defined in claim 15 wherein said casing has apertures axially aligned with said tubular conductors to permit wires to be inserted through said casing and into said tubular conductors from points located externally of the casing.
 17. An electrical receptacle for connecting a plug receptacle or a switch to a source of power, the receptacle comprising in combination; a plastic casing including a backwall and opposite sidewalls projecting forwardly from the backwall to define a compartment, a pair of tubular conductors extending longitudinally in the compartment adjacent the back- and sidewalls for receiving wires to establish a electrical connection therewith, said conductors each having adjustable means for releasably securing wires to the conductors respectively, two conductor prongs respectively secured to said conductors and projecting at an angle thereto, a third ground prong, means securing said ground prong in the compartment between said first two conductors, and a front wall closing the compartment in the casing, said front wall having a pair of apertures aligned with said conductor prongs for receiving the prongs of a wall switch or a plug receptacle for interengaging the latter with the conductor prongs in the compartment, said front wall having a third aperture aligned with said ground prong for receiving a ground prong of a wall switch or plug receptacle to interengage the latter with the ground prong in the casing.
 18. An electrical receptacle comprising a casing made of nonconductive material and defining a compartment, a hollow, metallic tubular conductor secured to the casing in said compartment for receiving wires, an adjustable conductor element, means mounting said adjustable conductor element in one wall of said tubular conductor for movement transversely of the axial direction of said tubular conductor for engaging a wire placed axially in the tubular conductor to hold the wire against a portion of said tubular conductor, said casing having an aperture in axial alignment with said tubular conductor to permit a wire to be inserted through the casing and into the tubular conductor from a point Externally of the casing.
 19. An electrical receptacle for connecting a plug receptacle or a switch to a source of power, the receptacle comprising in combination; a casing made from nonconductive material and having means defining a compartment, a pair of conductors in the compartment for connection to wires to establish electrical connection therebetween, said conductors each having means for releasably securing wires to the conductors respectively, two conductor prongs respectively secured to said conductors and projecting at an angle thereto, a third ground prong, means securing said ground prong in the compartment between said first two conductors, and a front wall closing the compartment, said front wall having a pair of apertures aligned with said conductor prongs for receiving the prongs of a wall switch or a plug receptacle for interengaging the latter with the conductor prongs in the compartment, said front wall having a third aperture aligned with said ground prong for receiving a ground prong of a wall switch or plug receptacle to interengage the latter with the ground prong and the casing. 